This invention relates to determining the dynamic modulus of materials and more particularly to a high-frequency dynamic indentation system for use with a commercial/custom made atomic force microscope (AFM) to extend analysis to higher frequencies.
Atomic force microscopes often include a piezoelectric actuator for dynamic indentation experiments on materials with time (frequency)-dependent mechanical properties such as cartilage to determine its dynamic modulus. For the case of cartilage, the frequency-dependent properties of the tissue can be used to detect GAG (Glycosamicoglycan)-depletion, which represents early stage arthritis.
The piezoelectric actuator in an AFM is not capable of high-frequency operation so that the complex dynamic modulus of cartilage, for example, cannot be sufficiently characterized. This information is needed in order to draw secondary conclusions about the sample under investigation, for example, to determine whether the cartilage is normal or GAG-depleted. The latter in this case would be an indication of the onset of arthritis.
It is therefore an object of the present invention to provide a secondary sample oscillation system to be used in conjunction with a commercial AFM that operates in a sufficiently high frequency range to enable proper characterization of the mechanical properties of the sample under investigation, for example, to distinguish normal cartilage from GAG-depleted cartilage. Of course, the system disclosed herein can be used with materials other than cartilage.